The title compound, C(21)H(36)O(3), was obtained by treatment of cyclo-hexa-necarbaldehyde with catalytic toluene-4-sulfonic acid monohydrate. This redetermination results in a crystal structure with significantly higher precision than the original determination [Diana & Ganis (1963 ▶). Atti Accad. Naz. Lincei, 35, 80-88]. The asymmetric unit contains one sixth of the mol-ecule, the formula unit being generated by crystallographic 3m symmetry. In the mol-ecule, the trioxane and cyclo-hexane rings are in chair conformations. In the crystal structure, mol-ecules are linked by weak C-H⋯O hydrogen bonds along the [001] direction.